如何修改此查询以省略空格或空值？

Question

This query is used to select distinct value from a table in the database

public List<SubDepartmentViewModel> GetSubDepartments()
{
    var query = _db.SendersReceivers.Select(a => new SubDepartmentViewModel
    {
        SubDepartmentName = a.SubDepartment //column in the database  
    })
    .Distinct().ToList();

    return query;
}

Answer 1

var query = _db.SendersReceivers
         .Where(a => !string.IsNullOrEmpty(a.SubDepartment))
         .Select(a => new SubDepartmentViewModel
                {
                  SubDepartmentName = a.SubDepartment

                })
         .Distinct().ToList();

This should do the trick.